Electronic component for high frequency power amplification

Abstract

An electronic component for high frequency power amplification realizes an improvement in switching spectrum characteristics. The gain of an amplifying NMOS transistor is controlled by a bias voltage on which a bias control voltage is reflected. Further, a threshold voltage compensator compensates for a variation in threshold voltage with variations in the manufacture of the amplifying NMOS transistor. The threshold voltage compensator includes an NMOS transistor formed in the same process specification as the amplifying NMOS transistor and converts a variation in current flowing through the NMOS transistor depending on the variation in the threshold voltage of the amplifying NMOS transistor to its corresponding voltage by a resistor to compensate for the bias voltage. It is thus possible to reduce variations in so-called precharge level brought to fixed output power in a region (0 dBm or less, for example) low in output power.

1. An electronic component for high frequency power amplification, comprising:
 a first transistor which amplifies a high frequency input signal with gain corresponding to a bias control signal and generates a high frequency output signal; 
 a power detector which detects output power of the high frequency output signal; 
 an error amplifier circuit which compares a result of detection by the power detector and an output level indication signal for setting a value of the output power from outside thereby to control the bias control signal; 
 a precharge circuit which controls the bias control signal in such a manner that the output power becomes a fixed value within a range in which the value of the output power becomes small up to such an extent as to be undetectable sufficiently by the power detector; 
 a voltage controller which applies a bias voltage corresponding to the bias control signal to the first transistor; and 
 a compensator including a monitoring transistor formed in the same process specification as the first transistor, the compensator detecting a change in electrical characteristics with a process variation having occurred even in the monitoring transistor in a manner similar to the first transistor and compensating for the bias voltage, based on the detected signal; 
 wherein the first transistor and the monitoring transistor are MIS transistors, and 
 wherein the process variation is indicative of a variation in threshold voltage. 
 
     
     
       2. The electronic component according to  claim 1 , wherein the voltage controller comprises:
 an amplifier which outputs a voltage proportional to the voltage of the bias control signal by a negative feedback configuration; and 
 first, second and third resistors coupled in series sequentially from an output node of the amplifier,
 wherein the bias voltage is generated from a coupling node of the second and third resistors, and 
 wherein the compensator causes a current of the monitoring transistor varied based on the variation in the threshold voltage to flow into a coupling node of the first and second resistors. 
 
 
     
     
       3. The electronic component according to  claim 2 , wherein the compensator comprises:
 the monitoring transistor; 
 a current transfer transistor which configures a current mirror circuit together with the monitoring transistor; 
 a fourth resistor whose one end is coupled to a drain of the monitoring transistor; and 
 a constant voltage circuit coupled to the other end of the fourth resistor, and
 wherein a drain of the current transfer transistor is coupled to the coupling node of the first and second resistors. 
 
 
     
     
       4. The electronic component according to  claim 1 , wherein the voltage controller comprises:
 an amplifier which negative feeds back a voltage of an output node thereof via resistance division based on a plurality of dividing resistors and outputs a voltage proportional to the voltage of the bias control signal; and 
 fifth and sixth resistors coupled in series sequentially from the output node of the amplifier,
 wherein the bias voltage is generated from a coupling node of the fifth and sixth resistors, and 
 wherein the compensator causes the current of the monitoring transistor varied based on the variation in the threshold voltage to flow into any coupling node between the dividing resistors. 
 
 
     
     
       5. The electronic component according to  claim 4 , wherein the compensator comprises:
 the monitoring transistor; 
 a current transfer transistor which configures a first current mirror circuit together with the monitoring transistor; 
 a second current mirror circuit which outputs a drain current of the current transfer transistor with the direction thereof being changed; 
 a seventh resistor whose one end is coupled to a drain of the monitoring transistor; and 
 a constant voltage circuit coupled to the other end of the seventh resistor, and
 wherein a current outputted from the second current mirror circuit is caused to flow into any coupling node between the dividing resistors. 
 
 
     
     
       6. The electronic component according to  claim 5 , wherein the compensator further comprises:
 an eighth resistor coupled between the drain and gate of the monitoring transistor; and 
 a ninth resistor coupled between the gate and source of the monitoring transistor. 
 
     
     
       7. An electronic component for high frequency power amplification, comprising:
 a plurality of stages of amplifiers which are coupled in tandem in plural stages and which amplify a high frequency input signal inputted to a first stage with gain corresponding to a bias control signal and generates a high frequency output signal from a final stage; 
 a first transistor which is included in the amplifier of the final stage and performs an amplifying operation; 
 a bias voltage controller which applies a bias voltage corresponding to the bias control signal to the first transistor; 
 a second transistor which is included in the amplifier of the first stage and performs an amplifying operation; 
 a bias current controller which supplies a bias current corresponding to the bias control signal to the second transistor by a current minor circuit; 
 a power detector which detects output power of the high frequency output signal; 
 an error amplifier circuit which compares a result of detection by the power detector and an output level indication signal for setting a value of the output power from outside thereby to control the bias control signal; 
 a precharge circuit which controls the bias control signal in such a manner that the output power is brought to a fixed value within a range in which the value of the output power becomes small up to such an extent as to be undetectable sufficiently by the power detector; and 
 a compensator including a monitoring transistor formed in the same process specification as the first transistor, the compensator detecting a change in electrical characteristics with a process variation having occurred even in the monitoring transistor in a manner similar to the first transistor and compensating for the bias voltage of the first transistor, based on the detected signal; 
 wherein the first transistor and the monitoring transistor are MIS transistors, and 
 wherein the process variation is indicative of a variation in threshold voltage. 
 
     
     
       8. The electronic component according to  claim 7 , wherein the bias voltage controller comprises an amplifier which outputs a voltage proportional to the voltage of the bias control signal by a negative feedback configuration, and first, second and third resistors coupled in series sequentially from an output node of the amplifier,
 wherein the bias voltage is generated from a coupling node of the second and third resistors, and 
 wherein the compensator causes a current of the monitoring transistor varied based on the variation in the threshold voltage to flow into a coupling node of the first and second resistors. 
 
     
     
       9. The electronic component according to  claim 7 , wherein the bias voltage controller comprises:
 an amplifier which negative feeds back a voltage of an output node thereof via resistance division based on a plurality of dividing resistors and outputs a voltage proportional to the voltage of the bias control signal; and 
 fifth and sixth resistors coupled in series sequentially from the output node of the amplifier,
 wherein the bias voltage is generated from a coupling node of the fifth and sixth resistors, and 
 
 wherein the compensator causes the current of the monitoring transistor varied based on the variation in the threshold voltage to flow into any coupling node between the dividing resistors.